The shortening of overall lengths of rack steering gears has always presented a problem. Thus in German patent DBP No. 11 37 328, the overall length of the construction is shortened by disposing the control valve in an axial bore of the power piston. The reciprocating drive of the steering mechanism connects to the ends of the piston rods. Due to the required length of stroke of the piston rod, there is insufficient space for the steering rods, particularly in vehicles with a narrow wheel base. Thus the steering rods must be made short and this is a disadvantage in the steering geometry. Another disadvantage in the patented arrangement is that the oil lines to the control valve provide sealing difficulties.
German patent OS No. 19 33 403 shows shortening of the overall arrangement by disposing the booster cylinder alonside the rack. The steering rods are attached at the ends of the rack by means of ball joints, and are relatively short. Additionally, the patented arrangement requires elements of the control valve to rotate with the steering spindle and the pinion which causes sealing problems.
German patent OS No. 20 32 183 shows an arrangement wherein the point of rotation of the ball bearings of the steering rod is inside the rack and shifted within the cylinder through a rolling diaphragm. The gain in length for the steering rods is relatively small.
German patent OS No. 21 14 591 shows an arrangement wherein the steering rods are attached to the rack approximately at the middle of the steering gear. Although the steering rods are not necessarily limited in length, the construction is expensive and the rigidity of the housing is reduced by the slots required for the steering rods.